Precipitating bath for viscose filaments



Patented Sept. 24, 1935 PRECIPITATING BATH FOR VISCOSE FILAMENTS JohannJoseph Stiickly and August Briitz, Teltow- Seehof,

Germany, assignors to North American Rayon Corporation, New York, N. Y.,a corporation of Delaware No Drawing. Application July 15, 1930, SerialNo. 468,197. In Germany July 15, 1929 3 Claims.

In the use of sulphuric acid-sodium sulphate baths as precipitatingmeans for extruded filamerits, it is well known that particularlydesirable products are obtained if the sodium sulphate is 5 present in asufiicient quantity to overcome the bi-sulphate reaction from thesulphuric acid present. In order to prevent loss of lustre and softnessand shrinking of the filaments, the use of the processes now knownnecessitate the application of tension to the filaments during thewashing and first drying step. This is indicated by the usual method ofwashing and drying the filaments while they are on the fixed take-up de-'vices, in the spool spinning, and glass-roller spinning machines. Whenthe so called centrifuged spinning process is used, installations ofstretching trucks, or the addition of other elements, is necessary.

According to the present invention, the use for any of these spools,glass-rollers, stretching or stiffening devices, etc., is done awaywith, and are not necessary in and treating (especially drying) thenewly spun filaments. When the well known Mueller bath discussed inparagraph one, is used,

together with the abridged treatment later described the two bathingredients above do not prevent shrinkage, loss of lustre and softness,etc. The use of a higher concentration of the salt solution will improvematters to a slight degree,

but crystallization of the salts with consequent damage to thefilaments, may result.

The present invention contemplates the addition of certain quantities ofzinc sulphate to the bath, this addition producing good results inobviating the defects above mentioned. Experience, however, has shownthat despite the addition of zinc sulphate, the sulphate concentrationof the bath must not sink below a certain minimum percentage ofsulphuric acid present, if

good results are to be obtained. Further, it has been discovered thatthe sodium sulphate concentration must not be allowed to drop to lessthan about 230 gr. NazSOr per liter. Although the concentration ofsodium sulphate may be increased, the best results are obtained whenabout 250 gr. Na2SO4 per liter are used.

The addition of the zinc sulphate, and the quantity of this salt to beadded, is important. For the best results, at least 5 gr./litre of ZnSO4should be present, although the exact percentage present is dependentupon the concentration of sulphuric acid used.

As a general rule, higher concentrations of sulphuric acid necessitatethe use of larger percentages of zinc sulphate. For example, it has beenfound that when grs. H2804 per liter and 250 gr. NazSOr per liter areused, 10 gr. of ZIlSOa must be added to give the best results.Similarly, for gr. H2804 per liter, 15 gr. ZnSOr per liter arenecessary. When still higher concentration 5 of sulphuric acid is used,for instance, 135 gr. H2804 per liter, 25 gr. ZnSO4 per liter arenecessary.

The addition of too great a percentage of ZnSO4 makes it necessary thatthe filaments contact 10 with the bath for a longer period of time.Otherwise, incomplete coagulation of the filaments results in theiragglutination. This latter difiiculty may be overcome or prevented byacidifying the newly spun thread before washing and dry- 15 mg.

This new process may be advantageously used with the centrifugalspinning method. The newly spun cakes are reeled in a wet and acidiccondition, and then washed in suitable washing machines, 20 treated, andhung up freely to dry. In this manner it is possible by eliminating thefirst washing and first drying, to obtain the skeins in one stroke.

In spite of this shortened process the yarn is not unduly shrunk, andpossesses the desired lustre 5 and softness.

Another advantage may arise from using this new process in thecentrifugal spinning method. The newly spun cakes may be washed,desulphurized, bleached, soaped, scoured, etc., without the 30 use ofany stiffening bodies, and these cakes may then be dried and. used forvarious purposes without the necessity of using any stiiiening bodies,or stretching.

35 Example Normal viscose containing 7% cellulose and 7% alkali, agedfrom 9-l0 I-Iottenroth, is spun into artificial silk of denier, 5 denierto the single 40 filament, by use of the usual metallic or nonmetallicspinnerettes. The following spinning bath is used;

110 gr. H2804 per liter,

250 gr. Na2SO4 per liter, 45

15 gr. ZnSO4 per liter,

dipping distance 20 cm.

If themachine used is the well known centrifugal spinning machine, thespun cakes are at once reeled in their wet and acidic condition, then 50thoroughly washed and dried without stretching. This method produces alustrous, soft, and not unduly shrunk yarn, especially when thedesulphurization step is completed,

We claim: 55

1. In a process for the manufacture of artificial filaments, yarns,threads, etc., from a viscose solution, the steps of preparing a normalviscose solution, and spinning it into a bath containing:

Gr/litre Sulphuric acid 110 Sodium sulphate 250 Zinc sulphate 15 andthen washing, after-treating and. drying the filaments, yarn, etc., inan unstretched condition. 2. In a process for the manufacture ofartificial filaments, yarns, threads, etc., from a viscose solution, thesteps of preparing a normal viscose solution, and spinning it into abath containing:

Per cent Sulphuric acid 8.25 to 10.71 Sodium sulphate 18.75 to 19.82

Zinc sulphate 0.825 to 1.98

Grams/liter Sulphuric acid 100 Sodium sulphate 230 Zinc sulphate 10 andthen treating the freshly extruded product and drying it Without theapplication of such tension as would cause stretching.

JOHANN JOSEPH s'rijcKLY. AUGUST BROTZ.

